[Oberon] syntax constrained editor: is Active Oberon LL1 ?

[Gérard Meunier]

Hello Patrick,

You may use Babel instead of Coco.

    http://www.oberon.ethz.ch/software/Babel.html

There are grammars already available for Oberon, Oberon 2 and AOS inside.
This version is a little old, but I can send you the last one if you are
interested.

Regards.

Gérard

----- Original Message ----- 
From: <Patrick.Hunziker at unibas.ch>
To: <oberon at lists.inf.ethz.ch>
Sent: Sunday, March 13, 2005 7:54 PM
Subject: [Oberon] syntax constrained editor: is Active Oberon LL1 ?


> I have had a look at building a syntax-constrained editor using the Oberon
> grammar and COCO.
> In principle, making the permitted text entries available at each caret
position
> is straightforward because they are anyway used for the parse tree at the
same
> location by COCO.
> I have encountered some unexpected hindrances, however:
> - Coco is slightly out of sync with the distributions it is found in.
> (CRA.Mod: "IF ch = r.eot" does not work, naturally).
> - I had problems finding an Oberon EBNF grammar which is LL1. I thought
the
> language is, in principle. However, the grammar at
> http://www.oberon.ethz.ch/EBNF.html  (*Oberon-1 ?*)
> is not, neither is
> the one in the distribution,
> neither is the one for Active Oberon at
> http://bluebottle.ethz.ch/languagereport/node7.html
> (I have not tried the Oberon-2 one at
>
http://statlab.uni-heidelberg.de/projects/oberon/kurs/www/Oberon2.EBNF.html
> and the one at
>
http://www.elegosoft.com/cgi-bin/cvsweb.cgi/m3/pm3/language/parsing/m3coco/test/misc/oberon.atg?rev=1.1.1.1&content-type=text/x-cvsweb-markup&cvsroot=PM3)
>
> In all these Cases Coco complained that there are LL1 inconsistencies in
the
> grammar, what could easily be confirmed visually.
> This might be a problem of reformulation, or a fundamental problem ??
> How do the compiler builders at ETH see this problem ?
> Below the example of the ActiveOberonGrammar.ATG and the Coco complaints.
> Greetings
> Pat
>
> COMPILER ActiveOberon (* A grammar for Active Oberon *)
>
> IMPORT Strings;
> VAR alternatives:ARRAY 1024 OF CHAR;
>
> CHARACTERS
>   eol      = CHR(13) .
>   letter   = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
>   digit    = "0123456789" .
>   hexDigit = digit + "ABCDEF" .
>   noQuote  = ANY - '"' - eol  .
>
> IGNORE  CHR(9) + CHR(10) + CHR(11) + CHR(12) + CHR(13)
>
> COMMENTS
>   FROM "(*" TO "*)" NESTED
>
> TOKENS
>   ident   =  letter { letter | digit } .
>   integer  =  digit { digit } | digit { hexDigit } "H" .
>   real  =  digit { digit } "." { digit }
>            [ ("E" | "D") [ "+" | "-" ] digit { digit } ] .
>   CharConstant = digit { hexDigit } "X" .
>   string  =  '"' { noQuote } '"' .
>
> PRODUCTIONS
> ActiveOberon           =  Module .
> Module = "MODULE" ident ";" [ImportList] {Definition} {DeclSeq} Body ident
> ".".
> ImportList = "IMPORT" ident [":=" ident] {"," ident [":=" ident ]} ";".
> Definition = "DEFINITION" ident ["REFINES" Qualident] {"PROCEDURE" ident
> [FormalPars] ";"} "END" ident.
> DeclSeq = "CONST" {ConstDecl ";"} | "TYPE" {TypeDecl ";"} | "VAR" {VarDecl
> ";"} | {ProcDecl ";"}.
> ConstDecl = IdentDef "=" ConstExpr.
> TypeDecl = IdentDef "=" Type.
> VarDecl = IdentList ":" Type.
> ProcDecl = "PROCEDURE" ProcHead ";" {DeclSeq} Body ident.
> ProcHead = [SysFlag] ["*" | "&"] IdentDef [FormalPars].
> SysFlag = "[" ident "]".
> FormalPars = "(" [FPSection {";" FPSection}] ")" [":" Qualident].
> FPSection = ["VAR"] ident {"," ident} ":" Type.
> Type = Qualident
>   | "ARRAY" [SysFlag] [ConstExpr {"," ConstExpr}] "OF" Type
>   | "RECORD" [SysFlag] ["(" Qualident ")"] [FieldList] "END"
>   | "POINTER" [SysFlag] "TO" Type
>   | "OBJECT" [[SysFlag] ["(" Qualident ")"] ["IMPLEMENTS" Qualident]
{DeclSeq}
> Body]
>   | "PROCEDURE" [SysFlag] [FormalPars].
> FieldDecl = [IdentList ":" Type].
> FieldList = FieldDecl {";" FieldDecl}.
> Body = StatBlock | "END".
> StatBlock = "BEGIN" ["{"IdentList"}"] [StatSeq] "END".
> StatSeq = Statement {";" Statement}.
> Statement = [Designator ":=" Expr
>   | Designator ["(" ExprList")"]
>   | "IF" Expr "THEN" StatSeq {"ELSIF" Expr "THEN" StatSeq}["ELSE" StatSeq]
> "END"
>   | "CASE" Expr "THEN" Case {"|" Case} ["ELSE" StatSeq] "END"
>   | "WHILE" Expr "DO" StatSeq "END"
>   | "REPEAT" StatSeq "UNTIL" Expr
>   | "FOR" ident ":=" Expr "TO" Expr ["BY" ConstExpr] "DO" StatSeq "END"
>   | "LOOP" StatSeq "END"
>   | "WITH" Qualident ":" Qualident "DO" StatSeq "END"
>   | "EXIT"
>   | "RETURN" [Expr]
>   | "AWAIT" "(" Expr ")"
>   | StatBlock
>     ].
> Case = [CaseLabels { "," CaseLabels } ":" StatSeq].
> CaseLabels = ConstExpr [".." ConstExpr].
> ConstExpr = Expr.
> Expr = SimpleExpr [Relation SimpleExpr].
> SimpleExpr = Term {MulOp Term}.
> Term = ["+"|"-"] Factor {AddOp Factor}.
> Factor = Designator["(" ExprList")"] | number | CharConstant | string
>   | "NIL" | Set | "(" Expr ")" | "~" Factor.
> Set = "{" [Element {"," Element}] "}".
> Element = Expr [".." Expr].
> Relation = "=" | "#" | "<" | "<=" | ">" | ">=" | "IN" | "IS".
> MulOp = "*" | "DIV" | "MOD" | "/" | "&" .
> AddOp = "+" | "-" | "OR" .
> Designator = Qualident { "." ident | "["ExprList"]" | "" | "(" Qualident
")"
> }.
> ExprList = Expr {"," Expr}.
> IdentList = IdentDef {"," IdentDef}.
> Qualident = [ident "."] ident.
> IdentDef = ident ["*"|"-"].
> number = real | integer .
> END ActiveOberon.
>
> -------------------
> Coco.Compile *
> Coco/R - Compiler-Compiler V2.2
>  checking
>   Case deletable
>   Statement deletable
>   StatSeq deletable
>   FieldDecl deletable
>   FieldList deletable
>   DeclSeq deletable
>   LL1 error in Designator: "(" is  start & successor of deletable
structure
>   LL1 error in Statement: ident is  start of several alternatives.
>   LL1 error in StatBlock: "END" is  start & successor of deletable
structure
>   LL1 error in Type: "END" is  start & successor of deletable structure
>   LL1 error in Type: "END" is  start & successor of deletable structure
>   LL1 error in Type: "END" is  start & successor of deletable structure
>   LL1 error in Type: "BEGIN" is  start & successor of deletable structure
>   LL1 error in ProcDecl: "END" is  start & successor of deletable
structure
>   LL1 error in ProcDecl: "BEGIN" is  start & successor of deletable
structure
>   LL1 error in Qualident: ident is  start & successor of deletable
structure
>   LL1 error in DeclSeq: "CONST" is  start of several alternatives.
>   LL1 error in DeclSeq: "TYPE" is  start of several alternatives.
>   LL1 error in DeclSeq: "VAR" is  start of several alternatives.
>   LL1 error in DeclSeq: "PROCEDURE" is  start & successor of deletable
structure
>   LL1 error in Module: "END" is  start & successor of deletable structure
>   LL1 error in Module: "BEGIN" is  start & successor of deletable
structure
>  +parser +scanner done
>
>
>
>
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